Recording your wavfiles

CLEAN YOUR RECORDS AS WELL AS POSSIBLE!! The safest method is to
use distilled water, and spray it on with a perfectly clean spray bottle.
Let it sit for a few minutes and then wipe it off with clean, soft, pure
cotton cloth. Don't do this on the turntable itself, lay the record on
a soft cloth on top of a firm flat surface. Any lint from the that
gets on the record from the cloth will come off easily with your regular
record duster that you will apply while the record is on the turntable
and spinning. There are plenty of places on the internet that have
suggestions for how to clean LP's. The other thing to try is to play
the LP once before you copy it to disk, the action of the needle in the
groove may be able to dislodge more remaining particles.

Make sure cpu and memory intensive apps are not running !!
For example the setiathome client uses enough of both to
really make the playback (and recording) not be able to
get data to and from the hard drive to the audio device.

Record your track(s). I now use a tool like brec for OSS and arec for ALSA, and
record a number of tracks (i.e. one entire side of an LP at
once). Because GWC can handle extremely large audio
files, it is more convenient to work with one single file.
Using cdrdao to burn the CD's also allows the use of a single
audio file.
Be sure to get some "silent" audio
at the start of each track, this information is used by gwc to assess the
background noise level for noise elimination.

An important note on GWC editing

GWC commits all changes to the original
file instantly, and undo saves the deltas needed to get back to the original,
so on exit all your changes are saved. As of version 0.21-06, GWC will
notify you that changes have been made, and give you the chance to exit (or open a new file)
without making the changes permanent.

Selecting regions

This is how you identify regions of audio for GWC to perform tasks upon, it is done by
highlighting a portion of the displayed audio waveform with the standard click and drag method using the mouse.

If you position your cursor between the left and right channels while you highlight, you will select both
channels, but if you move the cursor up or down when you make the selection, you can select either the left
channel, or the right channel indepedently.

There are 200 markers available. You set them by using the "B" and "E" keys, and clear them using the "Markers:Clear Markers" menu item.
"B" toggles the first marker at the start of the currently selected region. "E" toggles the second
marker at the end of the currently selected region.

While you are selecting a region, if the cursor gets within 10 pixels of a marker, it will "snap" to
that marker. This allows you to zoom in to a portion of the audio data, set a marker, zoom and pan to another
portion, set another marker, and then zoom back out and select the region between the markers -- giving you
a fine level of control on the precision of the selected region.

You may also press the 'm' key, to automatically select the region between markers. A button and icon are
in the works...

Steps to restore audio quality

Denoise

Select the sample region, make sure the sample region is entirely free of music.

If you have a "clean" LP, i.e. almost no crackle in the "silent" region
(you may the declicker in the silent region to remove a few clicks,
but make sure the result doesn't sound goofy)

Press the sample noise button (the one with the eyedropper)

Now select and
test denoising on a couple of different areas on the audio file, just to
be sure it works. Take the defaults of:

Try denoising a few seconds at the start of the track (include some of the pre-track
noise section to see how good the denoise algorithm works on pure noise). Play the
denoised region, see if you like it. Now do an Edit->undo (Ctrl-Z)

Repeat the above process at the end of the track and some place in the middle.
This gives you a good idea of how the noise sample a the start of the track will
work as an estimate of the actual noise at the middle and end of the track.

If you find the result sounds "metallic" or "burbly", back off on the reduction
amount, remember to use Edit->undo (Ctrl-Z). You can also try varying the gamma
factor. I have found if it gets too close to 1.0, it can distort the final
sound a little. Anything between 0.5 and 0.99 is probably worth trying.

When you are satisfied you have the settings you want, go for the gold and
select the entire track and denoise the whole thing. In most cases the defaults
given above will work quite well, so don't think this is hard, it's really easy!
At this point you may skip saving the undo data, which for most songs is 10's of megabytes and will take
some time to save.

Declicking

The highest quality declicking really needs to be done "manually". I have had cases where
it has a "false positive", and inadvertently degrades the signal in a few
places. I do manual declicking by either going to sonogram view,
and looking for spikes, or just listening and highlighting an area around
where I hear the click. There is no better click detector than your ears!
I have found for a window which is 600 pixels wide, about 22050 samples (about 1/2
second at the 44100 Hz sample rate, which is CD quality...)
displayed in the sonogram view works quite well.

There is an FFT click detector implemented now. The settings are the dB above
average that the click amplitude must be in order to be marked and or fixed.
Humans generally can detect a 3 dB change, so that's the default level for weak
click detection. While the FFT click detector appears to work better, it is
only based on some limited observations of mine, and it is MUCH SLOWER.

If you are working on a track that you are less concerned about the final quality,
then you can select a large region and use the declick strong clicks button. This
works reasonably well.

<HINT> - use the spacebar
to start and stop playback!!! left hand on
spacebar, right hand on mouse - very efficient. You can get a good
idea where the click is by watching where the cursor is when you hear
the click</HINT>

If you hit the "s" key during playback, gwc will stop
the playback and highlight the last 1/2 second of audio played

There are 3 levels of declicking

Declick-strong - searches for and repairs the loudest clicks

Declick-weak - searches for and repairs weaker clicks

Declick-manual - If neither of the above methods worked to find the click, you
can zoom in on the click by listening, highlighting, zooming in on the selection
as described above. Then, making sure you have only the damaged portion of the
audio data selected (in most cases this will be less than 100 samples), push this
button, and it repairs the highlighted selection (or current view) -- don't use on
more than about 200 samples!

In general you should start with Declick-strong , and use Declick-manual as your last resort.

De-crackling

-- that sound of bacon frying on your audio track. Crackle
is mostly a bunch of closely spaced clicks. First try the decrackling
algorithm. Use the default settings in preferences. If that fails you,
I have had success at times by repeatedly
applying the "remove strong clicks" filter over an area until the reported
repairs is zero.

Estimating

Sometimes, there are large sections in the audio (200 to 8000
samples), that are just bad. It may sound like a "thunk" or a dropout.
The estimation repair looks at the frequencies to the left and right of the
selection (or current view), and blends those frequencies across the repair
area. The result will be better than what was there to begin with,
as of version 0.20-08 this works quite well, but remember, UNDO is your friend!

Finishing up

Eliminate blank portions at start and end of track -- highlight the area
at the start of the track and use the scissors icon to indicate you want
that deleted, do the same for the end of the track. You can't eliminate
sections in the middle of the track. Umm, I haven't tested what would
happen if you tried, it could be bad. Always back up your data :-)

You may want to look at the reverb and DSP filters if the audio needs
a little bit of "presence". They are documented in the main help file for GWC

Exit. -- gwc will ask if you really want to save your changes

I wrote a little utility -- wavlist, which will list the *.wav files and
append the time in minutes:sec to the list so you can use it with something
like gcover to create jewel case covers.

KEYBOARD FUNCTIONS:

spacebar - starts and stops playback

'a' - Creates or appends "cdrdao.toc", with the currently selected or viewd audio segment.